1. Field of the Invention
The present invention relates to a mapping circuit of a CRT display device. More particularly, the present invention relates to a mapping circuit adapted to perform so-called texture mapping, namely, to map an arbitrary picture pattern onto planes representing a three-dimensional graphic on a CRT display device.
2. Description of the Related Art
In order to draw an arbitrary picture pattern, for example, oblique lines on each plane of a three-dimensional graphic represented on a CRT display device such as one used for computer-aided drafting (CAD), a technique called texture mapping is used. If texture mapping is applied, it is necessary to transform the picture pattern into coordinates on the planes representing the three-dimensional graphic on the CRT display in pixel units.
In case of applying texture mapping in a conventional CRT display device, coordinate transformation is made in pixel units by software processing in a host computer. However, if coordinate transformation is made in pixel units, it is necessary to make coordinate transformation for each of the pixels representing the three-dimensional graphic and accordingly the processing time becomes long, causing an increase in the workload of the host computer.